1. Field of the Invention
The invention relates to an earth drilling device designed with an auger, an encasing tube which surrounds the auger, a rotary drive for driving at least the auger in a rotating manner about a drilling axis, an ejecting device for discharging drill spoil from the auger, wherein the ejecting device has a discharge duct for the drill spoil, and a mast element along which the auger can be moved together with the ejecting device.
2. Related Art
A device for cased earth drilling is known for instance from JP 60-238516A. In this known drilling device, an ejection opening is provided at the upper end of the encasing tube below the rotary drill drive, through which the drill spoil conveyed by the auger can emerge. From the ejection opening the drill spoil falls along the encasing tube next to the drill tube to the ground. Since the ejection of drill spoil takes place on a level with the rotary drive, a great height of drop is present especially at the beginning of the drilling when the rotary drive is still located at a large distance from the ground. Therefore, special safety measures may be required to prevent accidents caused by drill spoil being dropped. In addition, the largely uncontrolled ejection of drill spoil on a level with the rotary drive can lead to considerable pollution of the construction site.
A generic earth drilling device is known from JP 06-257363 A. In this drilling device a flexible discharge bag is provided at the ejection opening, which forms a discharge duct for the drill spoil and guides the drill spoil when dropping down. An undirected swirling around of ejected drill spoil is thereby prevented so that the risk of accidents is reduced and pollution of the construction site is counteracted.
The discharge bag known from JP 06-257363 is designed such that it reaches to just above ground level when the drilling tool is withdrawn completely. This brings about a comparatively great length so that in windy weather conditions the fabric bag can move in an undesired way and get entangled in the device. Moreover, especially in the case of greater drilling depths a clogging of the bag may occur in particular if the drill spoil is humid and adheres to the bag.